Articles and Analysis

I have been focusing heavily on the Iowa caucuses, both our Disclosure Project
started with polls there and because the competition, particularly on the
Democratic side, is so intense. With a Democratic debate in Nevada
tonight, we have had two new polls out of "likely voters" in the Nevada Democratic
caucuses from Zogby
and CNN.** Their
results are quite different though for reasons that are probably explicable.

Both show Hillary Clinton leading, followed by Obama,
Edwards and Richardson, in that order, but the percentages are very different. CNN
shows Clinton
leading Obama by 28 points (51% to 23%), with Edwards far behind (at 11%). Zogby
shows Clinton
with a narrower, 22 point lead over Obama (37% to 19%) with Edwards closer (at
15%).

The biggest obvious difference is that the CNN survey
effectively pushed respondents harder for a choice. They show only 4% with no
opinion, while the Zogby shows 17% as unsure. This is a very common
source of variation across polls, leaving pollsters to debate which
approach - pushing for a choice or allowing uncertain voters to register their
indecision - is most appropriate when the election is still months away.

One likely contributor to that difference is that the CNN
questions includes the job title of each candidate ("New York Senator Hillary
Clinton," "Former North Carolina Senator John Edwards") which may frame the
question a bit differently. Of course, since Zogby fails to disclose the full
text of its vote question, we cannot know for certain.

But there is one other potential source of variation: How
the pollster handles the expected low turnout. The CNN release tells
us that they conducted 389 interviews with voters "who say they are likely to
vote in the Nevada
Democratic presidential caucus" out of a total sample of 2,084 adults. Thus,
CNN screens rather tightly to identify a Democratic sample that represents 19%
of Nevada
adults. Once again, as Zogby fails to disclose it, we have no idea what portion
of Nevada their sample represents (ditto for
Mason-Dixon, ARG and Research 2000, the three other pollsters that have
released Nevada
surveys).

But at 19%, even the CNN survey may be a shot in the dark at
the turnout in Nevada
on January 19. In 2004, Nevada
held traditional caucuses in mid-February that drew an estimate 9,000
participants (according to the Rhodes
Cook Letter). That amounts to roughly one half of one percent (0.5%) of the
state's voting age population at that time.

Of course, Nevada
is switching to a party-run primary (the main difference being far fewer
polling places). The states of Michigan and New Mexico have used a similar system, that produces a
higher turnout than traditional caucuses (outside Iowa) typically get, but not much higher. The
2004 Democratic turnout, as a percentage of the voting age population, was 2.2%
in Michigan and 7.3% in New
Mexico (both events occurred a week before Nevada
but a week after the New Hampshire
primary).

So who turns out this time is anyone's guess. Will the
voters sampled in these surveys bear any resemblance to those that turn out in Nevada on January 19? In
size, at least, that seems very unlikely.

**Zogby has also released results for likely Republican caucus-goers.
According to their release, CNN sampled likely Republican caucus-goers, but
they have not yet released those results.

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